A thick film is formed above a substrate in an electronic component such as a semiconductor device, in some cases. For example, an insulation film having a film thickness of micrometer order is sometimes formed on a substrate by a CVD (Chemical Vapor Deposition) method. However, when an underlying surface has steps, flatness of a deposited film is lowered according to the CVD method. Film flatness can be improved by a method of forming a fine particle film above a substrate, applying a polymer solution onto the fine particle film, and hardening the fine particle film and the polymer solution by heat treatment. However, when the fine particle film is formed to be thick, the polymer solution may be hardened, while the polymer solution has not penetrated the fine particle film to the bottom of the fine particle film or has penetrated the fine particle film only locally.